A mobile phone has been commonly spread and particularly, a folding type mobile phone having a foldable mechanism in which an upper housing and a lower housing are coupled to each other through a hinge portion has been widely spread in recent years. Folding type mobile phone generally have two postures of an opened posture and a closed posture, and has two advantages of being capable of enlarging a display screen when they are used in the opened state (in the opened posture) and thus improving usability, and of being capable of being transformed to a compact profile when they are used in the closed state (in the closed posture) and thus providing a portable convenience.
Recently, users have had more interest in the local average SAR and have a tendency to select mobile phones with a low local average SAR, using the local average SAR as an index of selection. Therefore, it is preferable for mobile phones to have a low local average SAR. A method of reducing the local average SAR have been known in the art, in which an electrical conductive metal element with an end open is connected (grounded) to a gland adjacent to a power feeding point in an unbalance-typed power feeding antenna and the element is set in a length to resonate at a desired frequency. Further, the element is disposed opposite to the side with opening of the receiving part of the housing that contacts the human housing. According to this configuration, current flows from the power feeding point to the electrical conductive metal element, so that it is possible to reduce the current flowing to the side that contacts the human housing (see Patent Document 1).
Further, according to another method of separating a current of a power feeding point in the art, a shield case of an upper housing with a receiving part in a folding type mobile phone is used as an antenna element (antenna 1), power is supplied to the antenna element through a flexible cable from a gland substrate of a lower housing, and a rod antenna (antenna 2) is connected with a power feeding portion (see Patent Document 2).
Configurations in the related art are shown in FIGS. 4 and 5. FIG. 4 shows a configuration with the housing open in the related art and FIG. 5 shows a configuration with the housing closed in the related art.
According to the examples in the related art shown in FIGS. 4 and 5, for example, according to Patent Document 1, an electrical conductive metal element with an end open is disposed adjacent to a hinge portion 103 that supports an upper housing 101 and a lower housing 102 of a folding type mobile phone 100 such that they are capable of opening/closing, and housing open/close detecting unit 104a, 104b that detects open/close of the bodies are provided. When it is detected that the bodies 101 and 102 are open, as shown in FIG. 4, a first matching circuit 106 connected with a first antenna 105 is connected to a wireless circuit 108 through an antenna switching circuit 107 and a second antenna 109 is connected to a gland pattern of a circuit board 111 through a switching circuit 110. Further, when it is detected that the bodies 101 and 102 are closed, as shown in FIG. 5, the second antenna 109 is connected to the wireless circuit 108 through a switching circuit 112 and an antenna switching circuit 113.
As described above, when the bodies 101 and 102 are opened, it is possible to reduce the local average SAR by separating the antenna current of the first antenna 105 to the second antenna 109. Further, resonant frequency of the second antenna 109 and the matching circuit 106 is constant at the transmitting frequency and the receiving frequency, regardless of the open/closed of the bodies 101 and 102.
Patent Document 1: JP-A-2002-353719
Patent Document 2: JP-A-2002-335180